Pneumatic tires

ABSTRACT

A pneumatic tire having a breaker, particularly of steel cord fabric and circumferential tread ribs provided with transverse slots extending across the whole or a major portion of the rib width to separate areas of tread rubber which will interlock to resist a sideways force applied to the tire, of which the following is a specification.

Patented July 31, 1973 FIG. I.

PNEUMATIC TIRES This invention relates to pneumatic tires particularlyto radial ply car tires.

In accordance with the invention a pneumatic tire comprises a tread, abreaker radially inwards of the tread, the tread having at least one ribextending in a substantially circumferential general direction, aplurality of narrow transversely-extending slots being provided in therib, each slot extending from one edge of the rib across the whole or amajor portion of the rib width, so as to separate or effectivelyseparate areas of tread rubber in the rib which will interlock one withanother to resist a transverse force applied to the tread.

Preferably, the pneumatic tire comprises a radial ply carcass, and thebreaker steel cord fabric.

Preferably also, the slots are of variable depth being shallower at theedge of the rib and have an average depth which is less than the ribheight.

A tire having features of the preceding paragraphs will have enhancedcircumferential flexibility compared with a tire havingcircumferentially continuous ribs since each rib is broken up intoseparate areas of tread rubber by the transverse slots while retaininggood lateral rigidity since the areas of rubber on each side of theslots interlock and provide resistance to lateral distortion ordisplacement forces.

The or each rib is preferably bounded by wide circumferentiallyextending grooves and is also provided with further slots and/orpin-hole like chambers. The grooves do not close up under normaloperating conditions of the tire, i.e., when the tire is inflated to itsnormal pressure and not overloaded, to drain from the contact patch thebulk of water displaced by the tire when running on wet ground while thethin film of water remaining between tire and ground surface is taken upby the slots and/or chambers to be released under centrifugal actionwhen the slots and/or chambers move out of the contact patch.

Two embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings FIGS. 1 and 2 whichrespectively show a plan view of the tread of two tires according to theinvention.

Each tire shown in the drawings comprises a radial ply car tire having abreaker of steel cords and a tread provided with wide, generallycircumferentiallyextending zig-zag main drainage grooves for drainingthe bulk of water from the contact patch.

Between each pair of adjacent circumferential grooves is defined acircumferentially-extending zigzag rib 11 provided with a plurality ofslots 12 and cylindrical holes 13 which soak up the thin film of waterremaining in the contact patch after the bulk water has been clearedthrough the wide grooves 10.

The ribs of tire shown in FIG. I are each provided with transversesinusoidal slots M which extend across the whole rib width to joinadjacent wide grooves 10, the junction between each sinusoidal slot andgroove occuring between groove apices 15. The sinusoidal form of eachslot 14 divides each rib 11 into blocks having curved edges, each ofwhich edges 16 interengage with a curved edge 17 of an adjacent block.

Under the influence of a transverse force, e.g. during cornering, eachblock in the contact patch will tend to be displaced axially and atleast part of each sinusoidal slot will close up so that an area oftread rubber adjacent the curved edge of one block will interlock withthe adjacent area of tread rubber in the adjacent block in a supportingaction to provide resistance to the transverse force. For example, thearea of rubber designated by reference number 16 will interlock with thearea of rubber 19 of the adjacent block.

Since the ribs are broken into blocks by the sinusoidal slots theflexibility of each rib in a circumferential direction will be increasedsimultaneously with providing rigidity in a transverse direction due tothe interlocking effect referred to in the preceding paragraph.

The ribs 11 of-the tire tread shown in FIG. 2 are each provied withpairs (20,21) of transversely extending zig-zag slots, each slotextending for approximately three quarters of the rib width, one slot 20in each pair extending form one side of a rib, the other slot, 21,extending from the opposite side of the rib. Each slot has only twolimbs and is arranged such that the limbs nearer the centre of the ribare parallel so as to define a narrow parallel-sided length 22 ofrubber, but nearer the edges of the rib the distance between the slotsin each pair increases so as to form approximately wedgeshaped areas 23,24 of rubber.

Under the influence of a side force the rubber in each rib 11 will tendto be displaced but the slots will at least partially close up, thewedge-shaped areas being supported by tread rubber on the other side ofslots. For example, the area 24 will be supported by an area 25 under asideways force. However, the circumferential flexibility of the ribswill be enhanced since the pairs of slots will act very similarly to asingle slot extending the whole rib width.

Good lateral rigidity in combination with circumferential flexibility isparticularly advantageous in a radial ply car tire having a treadreinforcement or breaker plies made from steel cords, the tire havingimproved stability, cooler running properties and improved tread life,the latter two of which are caused by the reduced distortion in thecontact patch and reduced scrubbing effect on approaching and leavingthe contact patch on account of the increased circumferentialflexibility. The provision of wide drainage grooves and further slotsand pin-hole like chambers improves the wet grip properties.

Having now described our invention what we claim is:

1. A pneumatic tire comprising a tread, a breaker radially inwards ofthe tread, the tread having at least one rib extending in acircumferential direction, a plurality of narrow generallytransversely-extending slots in the rib, each slot extending from oneedge of the rib across at least a major portion of the rib width so asto at least effectively separate areas of tread rubber in the rib whichwill interlock with adjacent areas of tread rubber to resist atransverse force applied to the tread in either direction.

' 2. A pneumatic tire according to claim I wherein each slot extendsacross the whole rib width to separate areas of tread rubber in the ribwhich will interlock one with another to resist a transverse forceapplied to the tread.

3. A pneumatic tire according to claim 1 wherein the breaker comprisessteel cord fabric.

4. A pneumatic tire according to claim 1 including a treadreinforcement.

5. A pnematic tire according to claim 4 wherein the tread reinforcementcomprises steel cord fabric.

6. A pneumatic tire according to claim 1 including a radial ply carcass.

7. A pneumatic tire according to claim 1 wherein the slots are ofvariable depth.

8. A pneumatic tire according to claim 1 wherein the depth of the slotsis shallower at the edge of the rib than elsewhere in the slot.

9. A pneumatic tire according to claim 1 wherein the average depth ofthe slots is less than the rib height.

10. 'A pneumatic tire according to claim 1 wherein the slots are ofsinusoidal configuration.

11. A pneumatic tire according to claim I wherein the slots are ofzig-zag configuration.

tend for the whole width of the rib.

1. A pneumatic tire comprising a tread, a breaker radially inwards ofthe tread, the tread having at least one rib extending in acircumferential direction, a plurality of narrow generallytransversely-extending slots in the rib, each slot extending from oneedge of the rib across at least a major portion of the rib width so asto at least effectively separate areas of tread rubber in the rib whichwill interlock with adjacent areas of tread rubber to resist atransverse force applied to the tread in either direction.
 2. Apneumatic tire according to claim 1 wherein each slot extends across thewhole rib width to separate areas of tread rubber in the rib which willinterlock one with another to resist a transverse force applied to thetread.
 3. A pneumatic tire according to claim 1 wherein the breakercomprises steel cord fabric.
 4. A pneumatic tire according to claim 1including a tread reinforcement.
 5. A pnematic tire according to claim 4wherein the tread reinforcement comprises steel cord fabric.
 6. Apneumatic tire according to claim 1 including a radial ply carcass.
 7. Apneumatic tire according to claim 1 wherein the slots are of variabledepth.
 8. A pneumatic tire according to claim 1 wherein the depth of theslots is shallower at the edge of the rib than elsewhere in the slot. 9.A pneumatic tire according to claim 1 wherein the average depth of theslots is less thaN the rib height.
 10. A pneumatic tire according toclaim 1 wherein the slots are of sinusoidal configuration.
 11. Apneumatic tire according to claim 1 wherein the slots are of zig-zagconfiguration.
 12. A pneumatic tire according to claim 1 wherein theslots are arranged in closely adjacent pairs defining a narrow portionof rubber therebetween.
 13. The tire of claim 1 in which thecircumferentially extending rib follows a zig-zag path and the slotsintersect the rib between apices of the rib.
 14. The tire of claim 1 inwhich the generally transversly-extending slots have a substantialportion of their length extending in a non-axial direction.
 15. The tireof claim 14 in which the slots do not extend for the whole width of therib.